To determine the significance of the heme biosynthetic pathway in RNA tumor virus-producing non-erythroid cell lines. To study the interrelationsips between malignancy, virus production and differentiation in Friend virusleukemia cells which can be stimulated to differentiate along the erythroid pathway by exposure to dimethylsulfoxide DMSO). To delineate biochemical defects in the genetic disease acute intermittent pophyria.